The study's objectives are to establish means to discover agents effective against fungal topoisomerases I and II. Long-term objectives are to implement a cell-based target-oriented search for inhibitors of topoisomerases of pathogenic fungi with complementary enzyme-based assays. Towards this effort we will devote our natural products resources based primarily on natural products from fungi. The test organisms to be used in these assays are the target organisms for which the drugs are intended, such as Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans. These fungal pathogens will be manipulated by molecular genetic means to disrupt specific genes so that they become highly sensitive to topoisomerase inhibitors. This study focuses on the C. albicans topoisomerase I. Preliminary studies, using C. albicans topoisomerase I, support the concept that species- specific inhibitors can be detected and that inhibition of topoisomerase I by a DNA-enzyme complex is sufficient in C. albicans to cause cell death. Furthermore, these studies indicate that an agent selective for C. albicans topoisomerase I that does not affect mammalian topoisomerase I can be detected. Implementation of a broad-scale search using the genetically engineered target-organisms provides an opportunity to exploit a new target in an area that is in dire need of new drugs.National Institute of Allergy and Infectious Diseases (NIAID)
